energy, as this dogmatic statement would have it supposed. It is only the principle of the final forms. The cycle of energy occasionally terminates in mechanical energy (phenomena of motion) and in a less degree in other energies; such as, for example, the electrical energy produced by the functional activity of the nerves and muscles in all animals, or in the functional activity of special organs in rays, torpedo-fish, and the malapterurus electricus, or finally, in the photic energy of phosphorescent animals. But these are secondary facts.
Heat is an Excretum.-The third principle of biological energetics may be therefore thus enunciated:—Vital energy in its final form becomes thermal energy. This principle teaches us that if chemical energy is the primitive generating form of vital energies, thermal energy is the form of waste, of emunctory, the degraded form as the physicists would say. Heat is in the dynamical order an excretion of animal life, as urea, carbonic acid and water, are excreta in the substantial order. By a false interpretation of the principle of the mechanical equivalence of heat, or through ignorance of Carnot's principle, certain physiologists have fallen into error when they still speak of the transformation of heat into motion or into into electricity in the animal organism. Heat is transformed into nothing in the animal organism. It is dissipated. Its utility arises not from its energetic value, but from the part it plays as a primer in the chemical reactions, as has been explained with reference to the general characteristics of chemical energy.
The Effect of Energetics on our Knowledge of the Relations of the Universe.—The consequences of these principles of energetic physiology, which give us so
